I am a guitarist for 62/years and started piano seriously at age 72. After two years of the challenge of transferring from guitar to piano, I had a real issue with playing the different fingering for both hands.
Not sure why but I closed my eyes one day and imagined the different fingering in my minds eye and it was much better. I only do this for the double octave scales. My teacher doesn’t even want me to do those yet so I thought maybe some of the teachers on this forum may have some insight into this . Thanks
How to practice octaves? Great question. Personally, I play them from the wrist, which I keep super-loose. Very, very slow, initially, with the metronome. If your span makes it comfortable, use the fourth finger on the black notes. List B Minor Sonata, or the last movement of Brahms B-flat piano concerto, where the octaves bounce around (not just scales), your arms have to "remember" where the hands are going. But even with scales, practice landing on the next note of the scale immediately following the previous octave, BEFORE playing it. Not sure why, but this very old technique seems to work with octave practice.
If your wrist gets tired or stiff, which it will, STOP and practice something completely different!
My 2 cents.